Tracksled EV Conversion

Hi Folks,

I’m planning to convert my Tracksled, basically an old snowmobile rear suspension (track/skid) with a predator 6.5 hp engine, to an electric sled. This vehicle is used to haul equipment (i.e., sled, wheel barrel) on trails’ year around but I mostly use this vehicle during winter to groom fat biking trails. The Tracksled weigh about 250 pounds and supposed to haul around 300 pounds or so. The vehicle's maximum speed is 15 mph. We usually use this vehicle to groom singletrack trails at a slow speed. So, I’m interested more in range than speed.

After searching around the forum, I was wondering if a 72V DC 3000W 45A motor with 50A controller should be enough. I'm thinking of three batteries in series ( 3x 24V ), probably something like some 2500mah 20A cells in a 7S3P setup.

This is my plan so far. Would be grateful for any advice.

Thanks,

Javier

What is the total distance you need to travel?

Voltage is top speed at wide open throttle.
Voltage also is related to total Wh which is your gas tank, same with Ah of the battery. Voltage x Ah = Wh so I rode with 36V 40A so the top speed was not that fast, and my hill climbing ability was limited due to not enough power (Wh) as compared to 52V 40Ah or 72V 40A. Especially so with the heavy weight, you totally notice Wh aka Power with the heavy weight. You may not want to go super fast, but you still want the power to climb hills at a decent speed. The faster you go up the hill the better, you wont burn up/cook the motor.

It'd be best to get a mid drive type motor, 5kw+
https://goldenmotor.bike/product-category/e-motorcycle-e-atv/
https://www.qsmotor.com/
https://www.cyclone-tw.com/

The cold temperature will have an effect on the batteries, so an insulated battery compartment.

Kelly Controller - https://www.kellycontroller.com

I'd go for 72V 50A (not Ah! We're talking Discharge Current, not Ah.) battery because thats what all the reputable battery builders use for a battery management control system.
72V 24Ah 50A Rectangular Lithium Battery CAD$1,325.00 - https://ebikes.ca/shop/electric-bicycle-parts/batteries.html?battery_nominal=142
or get EM3EV to build you a custom pack, say 72V 50A 60Ah
or buy a battery from an electric vehicle is an option.

Dont forget a battery charger, you can't get much better then Grin Satiator from Grintech at www.ebikes.ca, its the best charger you can buy!

Thanks, Markz!

We usually groom/pack around 5-6 miles of tight and twisty trails with some small climbs probably at 3-5 mph.

Because slow speeds at higher power levels can be death to a motor system that is actually setup for higher speeds, you're going to want to be sure the specific motor/etc combination you'll be using is good for the situation you're wanting to use it in. If it has a shiftable transmission between the motor and the track that might not be a problem...but if it doesn't, you may have to compromise on top speed to get hgiher power at lower speeds.

I would recommend going to http://ebikes.ca/tools/simulator.html and reading the entire page so you know what everything is and how it works, and then setup your tracksled conversion on there, using the MXUS 450x motor, which is probably the closest to a typical 3kw that has a heat model, but wont' be quite the same as what you'd use, assuming you're going with a chain or belt drive to the track (like the QSmotors 3kw "middrive" motor). Set it up as "middrive" with wahtever ratio you will use from it's output to the track.

Then whcihever controller comes closest to your desired controller if there is one, or "custom controller" if there isn't. Then the closest thing it has to your battery (or custom if it doesn't have one). It may take some experimentation to figure out what most closely matches what you have, but it is worht playing with for a while to do this.

Then check it's behavior in the expected terrain/wind/etc conditions, with varying abmounts of throttle (or autothrottle and set the speed you'd go on that terrain), the way you would typically ride it.

Observing the power usage and currents/etc for each condition with that setup will show you what it actually is taking to do what you want, and whether the motor is being hammered too much (heat rise, etc). Once you can see what it really takes to match your needs, you can then begin looking for a replacement motor (or system) that can easily handle what you throw at it, without breaking a sweat, as it were.



Regarding batteries...I recommend using a single pack to get the 72v, or at least a single BMS to protect all seriesed unprotected packs, because there can be issues with individually-bms'd seriesed packs should one of them shutdown, as the rest of the packs' voltage will be placed across it's FETs. If those FETs arent' high enough voltage, they can be damaged. There's ways ot protect agianst taht, too, but it's simpler to go with one BMS to protect all of them (which effectively makes them one higher voltage pack).